1. Field of the Invention
The present invention relates to a sound synthesizer system for producing a series of electrical signals which, after digital/analog conversion, can be applied to one or more transducers to produce an audible spectrum.
The invention concerns more particularly, although not exclusively, a sound synthesizer system of the type indicated above which can be used with the aid of a plug-in card which can be inserted into a personal computer to confer on it a very extensive and varied capacity to produce sounds.
2. Description of the Prior Art
The units most widely used at present to synthesize sound are known as "Wave Table" or "FM" units. In the "Wave Table" unit the sound is synthesized with the aid of groups of sound samples prestored in a rigid manner in a memory on any known recording medium, internal or external to the device.
In its simplest form, a "FM" unit uses two oscillations, one of which is a carrier which is frequency modulated by the other oscillation. This principle enables more complex oscillations to be generated by a limited number of oscillations. The signal obtained depends on the frequency ratios and on the amplitude of the modulating signals. The harmonics are the sidebands of the frequency modulation. These products have an equidistant frequency ratio proportional to the ratio between the modulating frequency and the carrier frequency. The amplitude of the modulatng signal determines the number of harmonics. The amplitudes of the harmonics produced cannot be determined freely and they follow a figure resembling an interference curve.
This means that "Wave Table" and "FM" units of the above type have the drawback of offering very little flexibility in terms of the modalities of composition of the final sound spectrum, the parameters characterizing the successive samples (amplitude, frequency and phase, in particular) being for the most part predefined without possibility of modification.
Also, these current sound synthesizer units operate with a computer, often a personal computer, and require frequent intervention by the computer. Being mobilized for this task continuously during the process of composition, processing and audio output, the computer cannot take care of housekeeping tasks, for example imaging or data acquisition tasks, other than those devoted to processing the data.
Finally, these prior art units are not very user-friendly and therefore do not lend themselves well to applications in multimedia installations which are currently expanding hugely among consumers.
The aim of the invention is to provide a sound synthesizer system which is free of the drawbacks of the prior art units briefly described above.